According to "Marks' Standard Handbook for Mechanical Engineers", 10th,
coal gas burns at about 3,590°F (1'977°C) under 100% air conditions. More or less
air will decrease the temperature.
This means that the maximum temperature of a coal fire in a forge is about 3,500°F (1'927°C).
Lower temperatures are given for boilers and furnaces because they don't want to melt the furnace and modern requirements want to reduce NOX emmisions.
Coal Quality - FAQ & Report by Glenn Conner AKA - NTECH
Here is an example from the Penn State coal sample database on our links page.
Seam : Pocahontas No. 3,
Type : Low Volitile Bituminous (lvb)
Ash : 7.44%
Volitile : 15.70%
Pocahontas No. 3 in Virginia has 15,006 BTU. AND another Pocahontas in West Virginia is 13,953. Not all Pocahontas coal is the same. . . But these are the best and something to compare to.
- Wednesday, 10/02/02 23:25:04 GMT
Jock's point that not all Pocahontas coal is the same is very valid.
A little history:
Pocahontas is the name of a seam of coal. NOT of a coal mine. The seam runs from somewhere in Kentucky (I think) through West Virginia and ends near Pittsburg, Pennsylvania. I for get how many different mines tap the Pocahontas seam, seems like it was about 30 or 40, but don't hold me to that.
NTech may be able to answer that for us.
The coal coming from each mine may be dramatically different, and sometimes even the coal from the same mine, but from different DAYS may be different. Again, if I remember correctly, Pocahontas #15 is among the more consistent.
NTech, please check this for accuracy, and correct as necessary.
- Wednesday, 10/02/02 23:47:06 GMT
A Little History of Coal, and Pocahontas #3 coal.
Time is the Carboniferous Period, which spans the period from 360 million years ago to 286 million years ago, about 70 millions before the dinosaurs.
The bottom half of this period is known in the U.S. as the Mississippian Period, the top half as the Pennsylvanian Period, and coal formed as the Mississippian Period ended and the Pennsylvanian Period started.
Coal seams are fossilized accumulations of plants which lived and died in swamps that were so devoid of oxygen that few microbes or other critters could survive to feed on their remains.
The first phase of coal known as "peat" thus developed.
These swamps were interwoven with intricate, meandering river channels which eventually covered things with mud and silt.
Subsequent deep burial by more sediments in succeeding geologic ages resulted in heat and pressure which transformed the peat into coal.
Generally speaking, every 12 inches of coal thickness represents approximately 10,000 years of continuous peat accumulation.
Coal seams in West Virginia average 3 feet in thickness, although they occassionally can be as thick as 25 feet.
The first reference to coal in what is today West Virginia in 1742, when John Peter Salley reported an outcropping of coal along a tributary of the Kanawha River.
By 1817, coal began to replace charcoal as a fuel for the numerous Kanawha River salt furnaces.
The total coal production in 1840 for the State was about 300,000 tons, of which 200,000 tons was used in the Kanawha salt furnaces.
Today West Virginia produces about 15% of total coal production in the U.S. and leads the nation in underground coal production.
West Virginia also leads the nation in coal exports with over 50 million tons shipped to 23 countries and accounts for 47% of US coal exports.
There are 117 named coal seams in West Virginia.
Sixty-five seams are considered mixable.
In the year 2000, coal was produced from 50 different coal seams.
Pocahontas Coal is broken down into 10 seams of Pocahontas coals, numbered #1 - #9 and Poca #3 rider.
Pocahontas 3,5,6,9, and 3 Rider are the seams that have listed coal production.
Total Pocahontas coal production was 7,697,193 tons or 4.72 per cent of total coal production.
If you consider just Pocahontas # 3, it produced 5,705,344 tons, which is 3.50 Per Cent of all coal production.
One interesting fact I came across in the search:
To move 2 megabytes of data on the internet, approximately one pound of coal is used.
Some of the references used to compile the above:
COKE: Coal with the volitiles cooked out of it. Similar to charcoal but denser. Used by foundries.
I'm trying to get started in blacksmithing but finding coal is a problem. However, we do have a cement plant close that burns enormous amounts of coke so I have an inexhaustable supply of this. Will using this coke work or should I go out of the way to find quality coal?
- Tuesday, 10/01/02 05:11:51 GMT
Brent, Coke like coal come in various grades. Generaly the heavy foundry coke is not suitable for use in a forge. AND, no matter what type of coke you use you MUST have a powered blower. Coke fires go out as soon as the air blast stops. So hand crank blowers and bellows are not suitable with coke. But it doesn't hurt to get a bucket full of the local coke and try it. But NEVER get more than a bucket full of an unknown fuel to test. Many smiths have 1 ton piles of various grades of coal taking up space on their lot. . .
Generaly you are better off ordering good coal or proper forging coke from Kayne and Sons and paying the shipping cost.
Many smiths travel hundreds of miles to obtain their coal.
Join your local ABANA chapter.
Many order coal in bulk and then resell to member's at cost.
If not, someone in the group may have a large truck and be handling coal or know where you can obtain it.
- Tuesday, 10/01/02 13:33:39 GMT
Coal vs. Charcoal:
North American ironmakers used charcoal for 100 years after mineral coal was in almost
universal use in England and most of Europe. The reason was sulfur. North America had the vast timber
reserves necessary to contiune using charcoal. The change finaly came as an logistic and ecconomic
neccesity. Making charcoal in huge quantities is a relatively slow process compared to mining coal. It was
also very expensive in manpower. It could not be made fast enough to smelt all the iron needed for a growing
Sulfur is not good in steel. However, the sulfur in coal used to forge steel has little effect unless the material is
thin and soaked a temperature for a long time. It is in the smelting process that sulfur is the big problem.
"Charcoal Iron" from Sweden was imported into the US well into the 1900's for special purposes.
- guru - Thursday, 06/14/01 15:51:08 GMT
FWIW--Charcoal -- Somewhere, years ago I read that Marco Polo was arrested and jailed on his return to Italy
for saying that the Chinese burned black stones (rocks) for a heat source.
If true, it would imply that mineral coal was unknown in Europe before that time !!!
grandpa - Thursday, 06/14/01 16:18:09 GMT
Coal and charcoal, part XXIV: During WWII swedish iron-smelting depended on charcoal. The story I have read
(Somewhere. . .) on mineral coal in medieval Europe was that it was known, you can pick it up from the
ground in certain areas, but considered poisonous and forbidden inside town limits.
Punishable by death, as I remember.
Olle Andersson - Thursday, 06/14/01 16:54:46 GMT
Coal to Charcoal Ratio: Charcoal has approximately the same fuel value per POUND as coal. Now. . if you
don't understand which weighs more, a pound of lead or a pound of feathers, then you are in trouble here.
Bituminous coal has a specific gravity of about 1.27.
Charcoal has a density of about 25% of the original wood. Pine and many woods used to make charcoal have a
density of about .5 (oak is .75 and white pine .4). So the average density of charcoal is .13 or about 1/10 that of
coal. Both have about the same percentage of ash. SO. . . it should take 10 times the volume of charcoal to do
the same job as coal. HOWEVER, coal contains a number of volatiles that required heat to evaporate and or
burn off. The volatiles help keep the coal burning but are driven off by the time you have coke for the center of
your fire. . . So the ratio between coal and charcoal is less for the blacksmith than for a furnace of a given BTU.
Should be about 8 to 9 times.
Now testing this would require some careful book keeping on fuel used relative to work done. But I suspect it is
- guru - Wednesday, 06/05/02 19:46:15 GMT
Charcoal Making Recipe #1
From Down Under (or ON TOP from the Aussie's point of view).
First dig a big hole, or talk some of your mates into doing it while you sit back and drink a beer.
Build a big bonfire in the hole.
When it is going good load it up with fresh wood but not higher than the edge of the hole.
Toss a sheet of corrogated steel roofing over the hole and seal the edges (with dirt from the hole).
Give it a few days to cool, open and remove charcoal.
Charcoal Making Recipe #2
Suburban backyard method.
First kill a chicken. . . WHOOPs wrong recipe.. .
Find a steel drum or "burn barrel" with a snug fitting lid or make a lid to fit.
The barrel should only have a few air holes near the bottom (no bigger than an inch).
Build a fire in the barrel.
When it is good and hot fill with fresh wood.
Let that start to char then cover the top (you might need to weight the lid).
Then close all but one air hole.
Sheet metal and dirt do this well.
Let cool for 24 to 36 hours. Open and remove charcoal.
See OErjan's method
Charcoal Making Recipe #3 Stove top (without dressing).
Fill a clean gallon paint can with blocks of wood (stick of willow if making artist's charcoal.
Close lid tightly.
The lid should have a nail hole to one side.
Set on top of stove burner and cook.
At some point the wood will burn briefly sending out a flair of flame and smoke from the vent hole. Continue cooking for about as long as it took to start burning, OR until wood gas fumes stop venting. Let cool overnight, open and remove charcoal. This method requires good ventilation and is not suitable in most modern kitchens. . Good reason for a stove in the shop.
NOTE 1: The above methods all take some practice and a little expertise but are proven methods that DO work.
There are two things to watch for.
A - burning up all the wood. You need to keep an eye on the venting.
B - not coaling long or well enough.
Save the half coaled stuff for starting the next batch.
You can also put the fire out with water if it gets out of control.
The charcoal still works when it dries out.
Using water on charcoal to extinguish it is NOT good.
True it WILL work almost as well as before when dry, BUT the water soluble parts of the
ashes, K2CO3 to name one (potash), will soak back in and give more ashes than usual
AND cause extra sparking (not sure why).
OErjan - Sunday, 03/31/02 12:14:23 GMT
Charcoal briquettes are mostly saw dust (hickory or mesquite for flavor)
and smoke more than the real stuff as well as producing more ashes and less BTU's.
They also contain some bituminous coal to keep the fire burning (that yummy sulfur taste).
When the Japanese Hibatchi is used for cooking with real charcoal there is very little or no smoke unless grease drips into the fire.
Commercial charcoal can be purchased from resturant suppliers.
- guru- Thursday, 03/21/02 (edited)
Does anyone have the details for making charcoal by the "pit burning" method?
Strangely enough, it does NOT involve any pit, nor any container or metal covering.
It was a mound of wood above ground, but I don't remember the exact details.
It was something I read about years ago when I was interested in blackpowder hunting.
Can anyone provide details?
- Saturday, 03/23/02 15:28:48 GMT
Taylor, Yes there is a "pit" method (see above).
The standard above ground bulk mound method was used for centuries.
For details see the Eric Sloan book, A Reverence for Wood
When charcoal was made in bulk a large quantity of trees were cut and stacked verticaly around a small hollow central core that was nearly closed at the top.
The stack was then covered with dirt to keep out the air.
The mound was often 30 feet high and 50 feet across.
Several vents were left open on the sides.
A prepared fire was started in the central core via the vent at the top.
Then the watching and maintaining started. . .
As the fire progressed and the stack settled openings would break through and need to be closed by climbing on top of the mound and sealing the hole.
VERY dangerous business.
If the fire became too intense the side vents would need to closed and the top vent made smaller.
If the fire got out of control there would be little charcoal.
If done properly very little wood burned (the volatiles feeding the fire) and there was a high percentage of charcoal.
The stack would need to be watched constantly for up to a month before it was sealed off to cool.
Making charcoal by this method was dangerous, dirty and took great skill.
It was also what fueled much of our early industry and in parts of Europe decimated forests.
The same method can be used on smaller scale but you get a lower percentage of charcoal.
- guru - Saturday, 03/23/02 16:24:26 GMT
Anyone out there know how to make charcoal?
Rob: Yes, I have a little knowledge (been making my own charcoal for several years). What do you
want to know? How to or what woods to use...(I'm guessing here)
As for how, burn wood with too little oxygen.
As to what wood, most woods except willow and related species, they make LOUSY coal with HUGE amounts of ashes.
I like alder, mountain ash (sorbus acoparia), oak, pine (pinus silvestris) and spruce (picea abies) in the order mentioned.
Old Swedish smiths preferred alder, pine and spruce, they (several old smiths I have interviewed) claimed the best was that left over from tar making.
As to how, check my brief charcoal making description on:
One thing is that the lid must NOT be completely air tight.
I made a mistake there. It should be near air tight.
But able to let smoke and steam OUT but NOT in.
Another thing is that the fire should burn but not too much.
I usually start with a little and when that catches throw on more wood (just so much that the small
fire wil get trouble keeping lit if I add 10-15% more) and let that catch and so on.
Hope it is of help
Örjan - Friday, 11/03/00 19:15:10 GMT
The guru-described charcoal mound method is also discussed in some detail in "Frontier Iron",
James D. Norris, 1964, The State Historical Society of Wisconsin, Worzalla Pub., Stevens Point, Wisc.
A diagram of the setup is shown on page 50. I've done it twice on a small scale. The mounds were
about 8 feet tall. Each time I got about an 80% yield, which I thought was pretty good for a
Frank Turley - Sunday, 03/24/02 12:37:32 GMT
The neo-tribal forums (see our links pages)
have had quite a lot on charcoal making by individuals; dig a little deeper!
Wood/charcoal is a very pure fuel compared to coal---*no* sulfur! Wood ash is a flux for forge
welding; however the efficiency goes way up if you can use charcoal instead of wood . . . you're not
wasting heat boiling off water and even more important *no* smoke!
Ever tried cooking over a smoky campfire where the smoke was always in your eyes?
Unless you have a good smoke extraction system your forge will resemble that.
So sure you can use it; but you will enjoy it a lot more if you can use charcoal. (after all charcoal was
the *only* fuel for about the first 2000 years of the iron age!)
Thomas Powers - Thursday, 03/21/02 21:59:09 GMT
I just made my first batch of charcoal! ( yellow pine )
It took about 3 or 4 hours and made loads of smoke. Does anyone know how to control or limit the smoke?
What wood does the best for converting to charcoal( hard or soft ) or is it better to mix wood types in the burn?
Also does anyone know a site or ref. book that has the general chemical process that is ocurring to the wood
during the 'charring '?
- Timex - Saturday, 04/23/05 23:08:39 EDT
coming off of your charcoal making operation is the volatile gasses and water in the wood. One way
to minimize the amount of smoke is to make your charcoal in a retort so that you can feed the volatiles into the
fire. Doing this allows the volatiles to be burned, reducing smoke, and it provides additional heat for the coalling
The simplest way to do this is to put your wood into a metal drum and close it up. The bung hole in the lid,
usually about 2" diameter, can be piped under the drum to feed the fire, or you can punch a few 1" holes in the
side of the drum. Either way, you heat the drum with a fire built below it, and have the gasses from the wood
feed into the fire.
When the wood has finished gassing off, you have done what you wanted and the result is charcoal. Let the fire
die down, or pull the drum away from the fire and let it cool. It is a good idea to put the holes in the drum on the
ground side to cover them during cooling, lest any glowing wood inside the drum use them to draw oxygen to
support combustion. If that happens, you end up with ash, not charcoal.
VIcopper CSI - Sunday, 04/24/05 07:28:16 EDT
see our Coal and Charcoal FAQ as weel as what VIc had to say above. Chemicaly there are some
VERY complex things going on in burning wood or making charcoal. The combination of cooking cellulose
reducing it to carbon while releaseing wood gas and burning the volatiles could fill a book on organic chemistry.
The type of wood also varies the chemistry.
Most production coalers feed the gases into the heating fire and burn them off. This greatly reduces the smoke
and coaling fuel costs. At a certain point the only fuel needed is the wood gas.
At the begining the process releases steam as water is driven off. Then the volatiles in the sap (you get
turpentine and pine tar from pine trees, sugars from maples and others) gases off making a lot of smoke. These
will burn with some help. At the end the cellouse (wood cell walls) is reduced to nearly pure carbon as the
hydrogen and a little carbon is driven off as wood gas. This last step is not carried out 100% as this is good fuel
but it results in hotter burning charcoal.
Coaling is done using a variety of methods. For an old fashioned charcoal pit see my recent article on Costa
Rica in our news.
- guru -
Sunday, 04/24/05 11:02:18 EDT
Coal Forges and Smoke Stacks:
I'm planning to build a blacksmith shop.
Someone told me about a telescoping counterbalanced stovepipe hood for my forge.
According to him, this is superior to the standard side draft hood.
He can't remember where he read about it, but thinks you might be able to refer me to the site.
Any help you can give me will be really appreciated.
The subject has come up numerous times but I have not seen plans for one.
Its pretty simple, A hood with stack that fits inside another., two cables pullies and counter weights.
The amount of counter weight depends on the size, shape weight, of the hood.
Nothing difficult to build except finding the telescoping pipe.
There is a distinct hazzard in using this type device.
If coal is piled on the forge (for the next day or to coke down) and the hood lowered there can be sufficient natural draft going through the small space or through the idle blower to create an out of control forge fire. I have a big rail road forge that this happened to.
A two foot hole in the bottom of the forge and the firepot were burned up.
I had to leave the blalanced hood due to 20 foot ceilings in the shop it was in and no access.
As over head hoods have too large an opening and almost always smoke the side draft type arrangement has become more popular because IT is superior.
I've recently had reports that stack turbines help a lot on forges with either type.
guru at anvilfire.com
Everything you need to know about mathematical hood and duct design is in a book called Industrial Ventilation
My 18th edition is Library of Congress Card Number 62-12929.
There is a table of "stack effect" numbers in Marks' Standard Handbook for Mechanical Engineers. The 8th edition is ISBN 0-07-004123-7 .
(most metal workers would find Marks' Handbook almost as useful as Machinery's Handbook).
Between the two, you can calculate stacks and hoods to your hearts content.
These are not easy calculations until you have done them a bunch of times.
I also suggest doing what the other guy has success with and scaling as necessary.
Just don't waste your time with a "smoke shelf".
Search the archives for arguments for and against them.
Also search for "stack effect", "stack".
And use a "low loss" stack cap
(defined in the archives) and not a "coolie cap" hat shaped stack cap.
250 cfm (cubic feet per minute) per square foot of stack opening at the fire would be a minimum face velocity for a side draft.
I'd be designing closer to 350 cfm/sq ft if you decide you like to crank numbers.
A hinged "door" at the top of a side draft opening helps direct the air into the side draft opening and can be swung up out of the way when necessary.
Olle, I know you said you were thinking non side draft, but that does seem the most popular.
An "elevator shaft" or straight stack coming down next to the fire is sort of like a side draft, but with a little less pressure loss.
Hot air rising up the stack is less dense that the surrounding shop air and the outside air and creates the pressure required to get the air to go up.
Reducing the pressure drop in the exhaust system (bigger pipe with less elbows) and having hotter gasses going up the stack will both increase flow up the stack.
If the pressure drop resisting the flow is greater than what the stack effect of less dense gasses can overcome, no air will go up the stack.
The fact that an overhead hood cools the stack gasses with lots of dilution air is why they don't work as well as a close fitting overhead or side draft.
- Thursday, 10/03/02 20:41:26 GMT
References and Links